The Scandinavian doesn't (out of the first 4 moves) lose tempo. After the black queen retreats both sides have one piece developed with white to move. However the black queen can potentially be kicked around if you're careless.

Watch some of GM Seirawan's STLCC Lectures on youtube. He has several games lectures/opening lectures, where he shows a side being down several tempo and the game goes just fine.

Good point, Seirawan seems to have no fear of losing a tempo in the opening if he can gain an advantage later but he stresses in 1 of his lectures that you can only do it in a Closed game, if the center is open you can't get away with it.

This is a great example, the French defence played with total disregard to developement & loss of Tempo

The Scandinavian doesn't (out of the first 4 moves) lose tempo. After the black queen retreats both sides have one piece developed with white to move. However the black queen can potentially be kicked around if you're careless.

Correct, and amazing how many people can't work this out. The queen moving twice is countered by the e pawn moving twice.